You are ignoring the long list of companies that modify the Linux kernel for their own purposes, never releasing their changes, and sometimes using their modified kernel on a web server that runs web apps for their users. As long as they are not distributing their modified kernel to anyone they can keep their changes secret.
For the same reason the GPLv2 has nothing to say about patents, even though patents are used to do the kinds of things the GPL was meant to prevent.
The thing to keep in mind is that the changes that web companies make to free software are not usually for internal consumption. The changes are user-facing -- but the software is delivered via the web, rather than distributed to the users, and so the web company never triggers any requirement to make their changes available. The GPL does allow this, but it is not in the spirit of the GPL, and the Affero GPL was created to deal with this problem.
I'm not sure that's true (I'm not the most knowledgeable person when it comes to the exact specifics of the GPL). Without institutions protecting IP (like patents, trademarks, copyright) the GPL couldn't exist, it's just a hack on top of IP.
I agree that it's not in the spirit of the GPL, but they did explicitly not add in sections about that in the GPLv3. The v2 FAQ mentioned that they were considering adding in web-based applications, but the v3 FAQ says it's still okay, but if you're writing software and want to make it not okay, use the AGPL.
> ...and untold millions of lines of changes to the Linux kernel are kept secret and are not at all available to other Linux users or even to Linux contributors. That is exactly the sort of the thing the GPL was meant to prevent.
It's false. Code that is modified and then never released is not what the GPL was meant to prevent.
It is not false in the context of the web being built on free software. The GPL is meant to prevent a situation where free software is used to create proprietary software that denies its users their freedom. In the case of web companies modifying free software and presenting their modified software to users as a web app, that is exactly what happens, and it is only because of a loophole that it does happen. The Affero GPL was created to address this particular loophole.
Along with the point you've just made, I thought about this after my last post, related to the difference between a tablet and the cloud. If a company changes the Linux kernel or an open-source application and includes it in their mobile device, they have to release the source on demand. As intended. (And there have been a number of high-profile cases in which companies tried to avoid releasing source.)
But if they change the Linux kernel or an open-source server utility and put it on their cloud server, they don't. An unintended outcome, and one that makes the cloud different than what came before it.
So I concede that the cloud is different, and it does affect the idea of open-source.
The line is drawn if and when a client machine downloads an open-source app from the cloud. If that never happens, then there's no requirement to release source.
